title: Oxidation-triggered ring-opening metathesis polymerization.
abstract: Eight new N-Hoveyda-type complexes were synthesized in yields of 67-92 % through reaction of [RuCl2 (NHC)(Ind)(py)] (NHC=1,3-bis(2,4,6-trimethylphenylimidazolin)-2-ylidene (SIMes) or 1,3-bis(2,6-diisopropylphenylimidazolin)-2-ylidene (SIPr), Ind=3-phenylindenylid-1-ene, py=pyridine) with various 1- or 1,2-substituted ferrocene compounds with vinyl and amine or imine substituents. The redox potentials of the respective complexes were determined; in all complexes an iron-centered oxidation reaction occurs at potentials close to E=+0.5 V. The crystal structures of the reduced and of the respective oxidized Hoveyda-type complexes were determined and show that the oxidation of the ferrocene unit has little effect on the ruthenium environment. Two of the eight new complexes were found to be switchable catalysts, in that the reduced form is inactive in the ring-opening metathesis polymerization of cis-cyclooctene (COE), whereas the oxidized complexes produce polyCOE. The other complexes are not switchable catalysts and are either inactive or active in both reduced and oxidized states.
authors.affiliation: Organometallic Chemistry, Technische Universität Darmstadt, Petersenstrasse 18, 64287 Darmstadt, Germany.
authors.forename: Roman
authors.initials: R
authors.lastname: Savka
authors.forename: Sabine
authors.initials: S
authors.lastname: Foro
authors.forename: Markus
authors.initials: M
authors.lastname: Gallei
authors.forename: Matthias
authors.initials: M
authors.lastname: Rehahn
authors.forename: Herbert
authors.initials: H
authors.lastname: Plenio
keywords: iron; olefin metathesis; oxidation; polymerization; ring-opening metathesis polymerization; ruthenium